Its class action head Andrew Watson said the claim, lodged in the NSW Supreme Court on Tuesday, expanded on an earlier class action, in which a court ruled that the late-payment fees were an unjustifiable, excessive penalty.

Mr Watson said members had to sign up to join the earlier action, which covered 185,000 customers of the various banks and was worth about $243 million.

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But he said the new legal claim would be much bigger, even though its actual size was to be determined.

"This action will be many times bigger because it will cover anyone who, at any stage, has been charged a late payment fee on a credit card," he said.

"It's too early to tell how it will stack up in terms of any compensation paid, but clearly in terms of the numbers of people involved, this is the largest class action in Australian history.

"We are really taking the fight to the banks on behalf of consumers, who have been levied, for years, these late payment fees."

Mr Watson said action against other banks was also on the cards.

"We will be taking action against other banks as we identify appropriate lead applicants who can lead up those actions."

He said that even though February's decision to award compensation for late-payment fees was subject to an appeal, due to be heard next week, it would not affect the decision to launch the current legal claim.

"This is not jumping the gun. This is an action which we have taken as part of a considered approach to ensuring that the rights of all customers of the banks are best preserved in the event that the appeal is successful," he said.

None of the banks contacted commented, while the Australian Bankers Association said it was not party to the proceeding and would not comment.